干旱区生态环境知识资源中心

Outbreaks of the predator crown-of-thorns starfish Acanthaster planci cause widespread coral mortality throughout the Indo-Pacific. Identifying mediating processes that promote coral survival during Acanthaster outbreaks can help support reef resilience. During surveys in French Polynesia, large colonies of the calcifying hydrozoan Millepora platyphylla appeared to be avoided by the starfish, providing predator-free sanctuaries to scleractinian corals in their proximity during an intense Acanthaster outbreak. Such refuges particularly benefited susceptible taxa such as Acropora and Pocillopora, whose populations were normally targeted by the starfish. These biological sanctuaries provided by Millepora to scleractinians are newly identified forms of associational refuges that can increase coral resistance to predation by Acanthaster. Our observations thus identify a key ecological role in reef resilience for Millepora, which is a ubiquitous component of tropical reefs usually seen as a strong competitor of scleractinians.